ANDOVER, Mass. -- David Hartman, who commanded an air defense battalion outside Tel Aviv during the Gulf War, remembers the thrill of watching a Patriot missile race into the sky and destroy an incoming Iraqi Scud.
He also remembers the sickening feeling when 28 U.S. soldiers were killed in a barracks in Saudi Arabia, after a Patriot system failed.
"Soldiers were depending on Patriot to protect them and it didn't," said Hartman, now an executive at Raytheon Corp., whose factory is churning out new Patriots in the event of a second war with Iraq. "That's our mission: not to let that happen again."
Since the 1991 war, the military has spent $3 billion to upgrade older Patriots, or Pac-2s, and develop a new version, called the Pac-3, which is built by Lockheed Martin Corp. but plugs into Raytheon radars and launchers.
While Pac-2s explode near targets and try to bring them down with shrapnel, the PAC-3 is designed to obliterate incoming missiles, such as Iraqi Scuds, by ramming them head-on.
Still, there are doubts that the anti-missile missile is up to the prodigious task of knocking Scuds out of the sky.
Politically, the Patriot was a hero of the Gulf War for keeping Israel out of the conflict and preserving the coalition. President George H.W. Bush visited the factory here to thank workers who built the missile.
But the Patriot's tactical achievements came under fire almost as soon as the shooting stopped.
The Army backed off initial claims that the Patriot successfully engaged 80 percent of the Scuds it was fired against. A congressional report concluded that Patriots downed Scuds just four times in 47 firings.
Massachusetts Institute of Technology missile expert Theodore Postol declared in 1991 there was no evidence the Patriots ever hit a Scud.
Would the Patriot perform better in a second war with Iraq? Raytheon says the improvements expand the "effective defended footprint" - i.e. the area the missiles can reliably protect - by a factor of seven over the Persian Gulf War.
Although Raytheon won't provide specifics, Gulf War-era Patriots were only designed to protect an airport-sized area from an incoming ballistic missile, said Tim Carey, Raytheon's vice president of the Patriot line.
"Now you can start thinking about protecting a metropolitan region," Carey said.
Raytheon has a lot riding on the Patriot's success. While it has a second shift working on upgrades for the U.S. order, foreign sales have been slow. The company told workers Wednesday it planned to lay off 300 people at the plant here.
Carey says the debate over the success rate is old news. Investigators found it almost impossible to determine whether Scuds were brought down by exploding Patriots or their own malfunctions.
But he acknowledges there were shortcomings. By the Army's count, the Patriot was 70 percent effective over Saudi Arabia and 40 percent over Israel. In revamping the Patriot, engineers have paid particular attention to the disparity.
Part of the explanation was that even missiles that may have been hit were still falling on populated suburbs in Israel. The first improvement was to build wireless launchers that can now be placed 19 miles from their radar and control trucks.
But the crux of the problem was that Scuds fired at Israel had farther to travel. They were launched higher and descended faster, pushing the number-crunching systems inside the Patriot to their limits.
Now, Raytheon says, those systems are far more powerful. Signals from Doppler pulse radar, installed in 1995, are processed by software that gives readings precise enough to distinguish between parts of a missile that breaks up in flight. It can steer the Patriot to the warhead.
"The software is a big thing," said Steve Zaloga, an analyst with the Teal Group, a defense consultancy. "Because the Army has spent the time and money over the last decade to deal with that issue, it will make a big difference."
Meanwhile, development of the interceptor missiles has split down two paths. Raytheon has been upgrading the old Pac-2 missiles, first designed for the easier task of downing aircraft.
Lockheed Martin won the contract to build the new Pac-3 interceptors.
The smaller Pac-3 was designed specifically with Iraqi Scuds in mind. It intercepts higher. It maneuvers better, using thrusters rather than fins. It destroys missiles with the force of impact, so it doesn't need a warhead.
The military, however, is likely to use a mix of air defense missiles. Only 52 Pac-3s have been delivered, and Raytheon has upgraded only a few hundred Pac-2s. The missiles could be used in combination, or, in Israel, as a second line of defense alongside that country's new Arrow missile defense system.
Raytheon says Patriots are being deployed in every country in the region surrounding Iraq where American troops are stationed, which would include Kuwait, Turkey, Saudi Arabia, Qatar and Bahrain.
And Steve Graham, Lockheed Martin's Pac-3 program manager, says "I have no qualms that this missile will do its job."
Others aren't so sure.
The Pac-3 intercepted a ballistic missile in each of its first seven tests. But each of the past four tests has had a shortcoming, ranging from firing failures to a "hit" that didn't destroy the target.
And the Pac-3 has never been tested against a Scud. Lockheed Martin says that's due to restrictions at the White Sands Missile Range. Postol calls the situation "unforgivable."
Experts say the Patriots may not even see action in a new conflict, given that Saddam Hussein is believed to have no more than 20 long-range missiles, and those may be so decrepit as to be unusable.
Engineers could still have years to continue tweaking the Patriots.
"The bad news is the Patriot is unlikely to do very well," Postol said. "The good news is these attacking missiles are not really a very large threat."